/* aes_encrypt.c - TinyCrypt implementation of AES encryption procedure */

/*
 *  Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *
 *    - Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *
 *    - Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 *    - Neither the name of Intel Corporation nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

#include <tinycrypt/aes.h>
#include <tinycrypt/utils.h>
#include <tinycrypt/constants.h>

static const uint8_t sbox[256] = {
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b,
    0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
    0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26,
    0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2,
    0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
    0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed,
    0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f,
    0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
    0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec,
    0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14,
    0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
    0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d,
    0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f,
    0x4b, 0xbd, 0x8b, 0x8a, 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
    0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11,
    0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f,
    0xb0, 0x54, 0xbb, 0x16
};

static inline unsigned int rotword(unsigned int a)
{
    return (((a) >> 24) | ((a) << 8)); // 24:byte alignment, 8:byte alignment
}

#define subbyte(a, o)(sbox[((a) >> (o))&0xff] << (o))
#define subword(a)(subbyte((a), 24)|subbyte((a), 16)|subbyte((a), 8)|subbyte((a), 0)) // 24:o, 16:o, 8:o

int tc_aes128_set_encrypt_key(TCAesKeySched_t s, const uint8_t *k)
{
    const unsigned int rconst[11] = { // 11:array length
        0x00000000, 0x01000000, 0x02000000, 0x04000000, 0x08000000, 0x10000000,
        0x20000000, 0x40000000, 0x80000000, 0x1b000000, 0x36000000
    };
    unsigned int i;

    if (s == (TCAesKeySched_t) 0) {
        return TC_CRYPTO_FAIL;
    } else if (k == (const uint8_t *) 0) {
        return TC_CRYPTO_FAIL;
    }

    for (i = 0; i < Nk; ++i) {
        s->words[i] = (k[Nb * i] << 24) | (k[Nb * i + 1] << 16) | // 24:byte alignment, 16:byte alignment
                      (k[Nb * i + 2] << 8) | (k[Nb * i + 3]); // 2:byte alignment, 8:byte alignment, 3:byte alignment
    }

    for (; i < (Nb * (Nr + 1)); ++i) {
        unsigned int t = s->words[i - 1];

        if ((i % Nk) == 0) {
            t = subword(rotword(t)) ^ rconst[i / Nk];
        }

        s->words[i] = s->words[i - Nk] ^ t;
    }

    return TC_CRYPTO_SUCCESS;
}

static inline void add_round_key(uint8_t *s, const unsigned int *k)
{
    s[0] ^= (uint8_t)(k[0] >> 24); // 24:byte alignment
    s[1] ^= (uint8_t)(k[0] >> 16); // 16:byte alignment
    s[2] ^= (uint8_t)(k[0] >> 8); // 8:byte alignment, 2:array element
    s[3] ^= (uint8_t)(k[0]); // 3:array element
    s[4] ^= (uint8_t)(k[1] >> 24); // 24:byte alignment, 4:array element
    s[5] ^= (uint8_t)(k[1] >> 16); // 16:byte alignment, 5:array element
    s[6] ^= (uint8_t)(k[1] >> 8); // 8:byte alignment, 6:array element
    s[7] ^= (uint8_t)(k[1]); // 7:array element
    s[8] ^= (uint8_t)(k[2] >> 24); // 2:array element, 24:byte alignment, 8:array element
    s[9] ^= (uint8_t)(k[2] >> 16); // 2:array element, 16:byte alignment, 9:array element
    s[10] ^= (uint8_t)(k[2] >> 8); // 2:array element, 8:byte alignment, 10:array element
    s[11] ^= (uint8_t)(k[2]); // 2:array element, 11:array element
    s[12] ^= (uint8_t)(k[3] >> 24); // 3:array element, 24:byte alignment, 12:array element
    s[13] ^= (uint8_t)(k[3] >> 16); // 3:array element, 16:byte alignment, 13:array element
    s[14] ^= (uint8_t)(k[3] >> 8); // 3:array element, 8:byte alignment, 14:array element
    s[15] ^= (uint8_t)(k[3]); // 3:array element, 15:array element
}

static inline void sub_bytes(uint8_t *s)
{
    unsigned int i;

    for (i = 0; i < (Nb * Nk); ++i) {
        s[i] = sbox[s[i]];
    }
}

#define triple(a)(_double_byte(a)^(a))

static inline void mult_row_column(uint8_t *out, const uint8_t *in)
{
    out[0] = _double_byte(in[0]) ^ triple(in[1]) ^ in[2] ^ in[3]; // 2:array element, 3:array element
    out[1] = in[0] ^ _double_byte(in[1]) ^ triple(in[2]) ^ in[3]; // 2:array element, 3:array element
    out[2] = in[0] ^ in[1] ^ _double_byte(in[2]) ^ triple(in[3]); // 2:array element, 3:array element
    out[3] = triple(in[0]) ^ in[1] ^ in[2] ^ _double_byte(in[3]); // 2:array element, 3:array element
}

static inline void mix_columns(uint8_t *s)
{
    uint8_t t[Nb * Nk];
    mult_row_column(t, s);
    mult_row_column(&t[Nb], s + Nb);
    mult_row_column(&t[2 * Nb], s + (2 * Nb)); // 2:byte alignment
    mult_row_column(&t[3 * Nb], s + (3 * Nb)); // 3:byte alignment
    (void) _copy(s, sizeof(t), t, sizeof(t));
}

/*
 * This shift_rows also implements the matrix flip required for mix_columns, but
 * performs it here to reduce the number of memory operations.
 */
static inline void shift_rows(uint8_t *s)
{
    uint8_t t[Nb * Nk];
    t[0]  = s[0];
    t[1] = s[5]; // 5:array element
    t[2] = s[10]; // 10:array element, 2:array element
    t[3] = s[15]; // 15:array element, 3:array element
    t[4]  = s[4]; // 4:array element
    t[5] = s[9]; // 9:array element, 5:array element
    t[6] = s[14]; // 14:array element, 6:array element
    t[7] = s[3]; // 3:array element, 7:array element
    t[8]  = s[8]; // 8:array element
    t[9] = s[13]; // 13:array element, 9:array element
    t[10] = s[2]; // 10:array element, 2:array element
    t[11] = s[7]; // 7:array element, 11:array element
    t[12] = s[12]; // 12:array element
    t[13] = s[1]; // 13:array element
    t[14] = s[6]; // 6:array element, 14:array element
    t[15] = s[11]; // 11:array element, 15:array element
    (void) _copy(s, sizeof(t), t, sizeof(t));
}

int tc_aes_encrypt(uint8_t *out, const uint8_t *in, const TCAesKeySched_t s)
{
    uint8_t state[Nk * Nb];
    unsigned int i;

    if (out == (uint8_t *) 0) {
        return TC_CRYPTO_FAIL;
    } else if (in == (const uint8_t *) 0) {
        return TC_CRYPTO_FAIL;
    } else if (s == (TCAesKeySched_t) 0) {
        return TC_CRYPTO_FAIL;
    }

    (void)_copy(state, sizeof(state), in, sizeof(state));
    add_round_key(state, s->words);

    for (i = 0; i < (Nr - 1); ++i) {
        sub_bytes(state);
        shift_rows(state);
        mix_columns(state);
        add_round_key(state, s->words + Nb * (i + 1));
    }

    sub_bytes(state);
    shift_rows(state);
    add_round_key(state, s->words + Nb * (i + 1));
    (void)_copy(out, sizeof(state), state, sizeof(state));
    /* zeroing out the state buffer */
    _set(state, TC_ZERO_BYTE, sizeof(state));
    return TC_CRYPTO_SUCCESS;
}